CHAPTER ONE
EVOLUTION AND THE NATURE OF SCIENCE

The scientific evidence supporting biologicalevolution continues to grow at a rapid pace.

For more than a century and a half, scientists have been gathering evidence that expands our understanding of both the fact and the processes of biological evolution. They are investigating how evolution has occurred and is continuing to occur.

In 2004, for example, a team of researchers made a remarkable discovery. On an island in far northern Canada, they found a four-foot-long fossil with features intermediate between those of a fish and a four-legged animal. It had gills, scales, and fins, and it probably spent most of its life in the water. But it also had lungs, a flexible neck, and a sturdy fin skeleton that could support its body in very shallow water or on land.

Earlier scientific discoveries of fossilized plants and animals had already revealed a considerable amount about the environment in which this creature lived. About 375 million years ago, what is now Ellesmere Island in Nunavut Territory, Canada, was part of a broad plain crossed by many meandering streams. Trees, ferns, and other ancient plants grew on the banks of the streams, creating a rich environment for bacteria, fungi, and simple animals that fed on decaying vegetation. No large animals yet lived on the land, but Earth’s oceans contained many species of fish, and some of those species fed on the plants and animals in shallow freshwater streams and swamps.

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chapter one
evolution
and the nature
of Science
the scientific evidence supporting biological
evolution continues to grow at a rapid pace.
For more than a century and a half, scientists have been gathering evidence
that expands our understanding of both the fact and the processes of biological
evolution. They are investigating how evolution has occurred and is continuing
to occur.
In 2004, for example, a team of researchers made a remarkable discovery.
On an island in far northern Canada, they found a four-foot-long fossil with
features intermediate between those of a fish and a four-legged animal. It had
gills, scales, and fins, and it probably spent most of its life in the water. But it
also had lungs, a flexible neck, and a sturdy fin skeleton that could support its
body in very shallow water or on land.
Earlier scientific discoveries of fossilized plants and animals had already
revealed a considerable amount about the environment in which this creature
lived. About 375 million years ago, what is now Ellesmere Island in Nunavut
Territory, Canada, was part of a broad plain crossed by many meandering
[species: In sexual­
streams. Trees, ferns, and other ancient plants grew on the banks of the streams,
ly reproducing organ­
creating a rich environment for bacteria, fungi, and simple animals that fed on
isms, species consist
decaying vegetation. No large animals yet lived on the land, but Earth’s oceans of individuals that can
contained many species of fish, and some of those species fed on the plants and interbreed with each
animals in shallow freshwater streams and swamps. other.]
Science, evolution, and creationiSm 1

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[Paleontologist: Paleontologists had previously found the fossils of some of these shallow-
water fishes. The bones in their fins were sturdier and more complex than in
A scientist who
studies fossils to other fish species, perhaps allowing them to pull themselves through plant-
learn about ancient filled channels, and they had primitive lungs as well as gills. Paleontologists
organisms.]
had also found, in somewhat younger sediments, fossils of fishlike animals
that likely spent part of their time on land. Known as early tetrapods (a
Paleontologists
word referring to their four legs), they had modified front and back fins that
searched this valley
resembled primitive legs and other features suited for life out of the water. But
in Nunavut, near the
paleontologists had not found fossils of the transitional animals between shal-
Arctic Circle in north
central Canada, for low-water fishes and limbed animals.
fossils when they
The team that discovered the new fossil decided to focus on far northern
learned that it con-
Canada when they noticed in a textbook that the region contained sedimentary
tained sedimentary
rock deposited about 375 million years ago, just when shallow-water fishes
rocks deposited dur-
ing the period when
were predicted by evolutionary science to be making the transition to land. The
limbed animals were
team had to travel for hours in planes and helicopters to reach the site, and they
first starting to live
could work for just a couple of months each summer before snow began to fall.
on land. Fossils of
Tiktaalik were dis- In their fourth summer of fieldwork they found what they had predicted they
covered on the dark
would find. In an outcropping of rock on the side of a hill, they uncovered the
outcropping of rock
fossil of a creature that they named Tiktaalik. (The name means “big freshwater
on the right side of
fish” in the language of the Inuit of northern Canada.) Tiktaalik still had many
this photograph.
site of fossils
Tiktaalik’s left and right fins had a single
upper bone (the large bone at the bot-
tom of each of these drawings) followed
by two intermediate bones, giving the
creature an elbow and a wrist, as in more
recent organisms.
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Tiktaalik lived during the
period when freshwa-
ter fishes were evolving
Ichthyostega the adaptations that
enabled four-legged
animals to live out of
water. Tiktaalik may have
lived somewhat before
Tiktaalik
or somewhat after the
ancestral species that
gave rise to all of today’s
limbed animals, including
Panderichthys humans. The evolution-
ary lineage that contained
Tiktaalik may have gone
extinct, as shown in this
diagram by the short line
branching from the main
evolutionary lineage, or
it may have been part
of the evolutionary line
leading to all modern
tetrapods (animals with
four legs). The last com-
mon ancestor of humans
and all modern fishes also
gave rise to evolution-
ary lineages that led to
modern lobe-finned fishes
of the features of fish, but it also had traits characteristic of early tetrapods. (represented today by
Most important, its fins contained bones that formed a limb-like appendage that the coelacanth). In this
and succeeding figures,
the animal could use to move and prop itself up.
time is represented by the
A prediction from more than a century of findings from evolutionary biol- lengths of the lines; mod-
ogy suggests that one of the early species that emerged from the Earth’s oceans ern groups of organisms
are listed at the top of
about 375 million years ago was the ancestor of amphibians, reptiles, dino-
the figure.
saurs, birds, and mammals. The discovery of Tiktaalik strongly supports that
prediction. Indeed, the major bones in our own arms and legs are similar in
overall configuration to those of Tiktaalik.
The discovery of Tiktaalik, while critically important for confirming predic-
tions of evolution theory, is just one example of the many findings made every
year that add depth and breadth to the scientific understanding of biological
evolution. These discoveries come not just from paleontology but also from
physics, chemistry, astronomy, and fields within biology. The theory of evolu-
tion is supported by so many observations and experiments that the overwhelm-
ing majority of scientists no longer question whether evolution has occurred and
continues to occur and instead investigate the processes of evolution. Scientists
are confident that the basic components of evolution will continue to be sup-
ported by new evidence, as they have been for the past 150 years.
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Biological evolution is the central
organizing principle of modern biology.
[trait: The study of biological evolution has transformed our understanding of life
A physical
or behavioral on this planet. Evolution provides a scientific explanation for why there are so
characteristic of many different kinds of organisms on Earth and how all organisms on this plan-
an organism.]
et are part of an evolutionary lineage. It demonstrates why some organisms
[DnA: that look quite different are in fact related, while other organisms that may look
Deoxyribo­
similar are only distantly related. It accounts for the appearance of humans on
nucleic acid. A biolog­
Earth and reveals our species’ biological connections with other living things. It
ical molecule composed
of subunits known details how different groups of humans are related to each other and how we
as nucleotides strung acquired many of our traits. It enables the development of effective new ways
together in long chains.
to protect ourselves against constantly evolving bacteria and viruses.
The sequences of these
Biological evolution refers to changes in the traits of organisms over multiple
nucleotides contain the
generations. Until the development of the science of genetics at the beginning
information that cells
of the 20th century, biologists did not understand the mechanisms responsible
need in order to grow,
to divide into daughter for the inheritance of traits from parents to offspring. The study of genetics
cells, and to manufac­ showed that heritable traits originate from the DnA that is passed from one
ture new proteins.]
generation to the next. DNA contains segments called genes that direct the pro-
[Protein: duction of proteins required for the growth and function of cells. Genes also
A large
orchestrate the development of a single-celled egg into a multicellular organism.
molecule consisting of
DNA is therefore responsible for the continuity of biological form and function
a chain of smaller mol­
ecules called amino across generations.
acids. The sequence However, offspring are not always exactly like their parents. Most organ-
of amino acids and
isms in any species, including humans, are genetically variable to some extent.
the molecule’s three­
In sexually reproducing species, where each parent contributes only one-half
dimensional structure
of its genetic information to its offspring (the offspring receives the full amount
determine a protein’s
of genetic information when a sperm cell and an egg cell fuse), the DNA of the
specific function in
cells or organisms.] two parents is combined in new ways in the offspring. In addition, DNA can
undergo changes known as mutations from one generation to the next, both in
[mutation: A change sexually reproducing and asexually reproducing organisms (such as bacteria).
in the sequence of
When a mutation occurs in the DNA of an organism, several things can
nucleotides in DNA.
happen. The mutation may result in an altered trait that harms the organism,
Such changes can alter
making it less likely to survive or produce offspring than other organisms in
the structure of pro­
teins or the regulation the population to which it belongs. Another possibility is that the mutation
of protein production.] makes no difference to the well-being or reproductive success of an organ-
ism. Or the new mutation may result in a trait that enables an organism to
[Population:
take better advantage of the resources in its environment, thereby enhancing
A group of organisms
its ability to survive and produce offspring. For example, a fish might appear
of the same species that
with a small modification to its fins that enables it to move more easily through
are in close enough
proximity to allow shallow water (as occurred in the lineage leading to Tiktaalik); an insect might
them to interbreed.]
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acquire a different shade of color that enables it to avoid being seen by preda-
tors; or a fly might have a difference in its wing patterns or courtship behav-
iors that more successfully attracts mates.
If a mutation increases the survivability of an organism, that organism is like-
ly to have more offspring than other members of the population. If the offspring
inherit the mutation, the number of organisms with the advantageous trait will
increase from one generation to the next. In this way, the trait — and the genetic
material (DNA) responsible for the trait — will tend to become more common
in a population of organisms over time. In contrast, organisms possessing a
harmful or deleterious mutation are less likely to contribute their DNA to future
generations, and the trait resulting from the mutation will tend to become less
frequent or will be eliminated in a population. Evolution consists of changes in
the heritable traits of a population of organisms as successive generations replace
one another. It is populations of organisms that evolve, not individual organisms.
The differential reproductive success of organisms with advantageous traits
[natural selection:
is known as natural selection, because nature “selects” traits that enhance
Differential survival
the ability of organisms to survive and reproduce. Natural selection also can
and reproduction
reduce the prevalence of traits that diminish organisms’ abilities to survive
of organisms as a
and reproduce. Artificial selection is a similar process, but in this case humans
consequence of the
rather than the environment select for desirable traits by arranging for animals characteristics of the
or plants with those traits to breed. Artificial selection is the process responsible environment.]
for the development of varieties of domestic animals (e.g., breeds of dogs, cats,
and horses) and plants (e.g., roses, tulips, corn).
Evolution in Medicine: Combating New Infectious Diseases
In late 2002 several hundred Immediately, work began on a
people in China came down blood test to identify people with
with a severe form of pneu- the disease (so they could be
monia caused by an unknown quarantined), on treatments for
infectious agent. Dubbed the disease, and on vaccines to
“severe acute respiratory syn- prevent infection with the virus.
drome,” or SARS, the disease An understanding of evolu-
soon spread to Vietnam, Hong tion was essential in the identi-
Kong, and Canada and led to fication of the SARS virus. The
hundreds of deaths. In March genetic material in the virus
2003 a team of researchers at was similar to that of other
the University of California, San viruses because it had evolved
Francisco, received samples of from the same ancestor virus.
a virus isolated from the tissues of a SARS patient. Furthermore, knowledge of the evolutionary history
Using a new technology known as a DNA micro- of the SARS virus gave scientists important informa-
array, within 24 hours the researchers had identi- tion about the disease, such as how it is spread.
fied the virus as a previously unknown member of Knowing the evolutionary origins of human patho-
a particular family of viruses — a result confirmed gens will be critical in the future as existing infectious
by other researchers using different techniques. agents evolve into new and more dangerous forms.
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Evolution in Agriculture: The Domestication of Wheat
When humans understand a phenomenon that wild wheat so that seeds remained on the plant
occurs in nature, they often gain increased control when ripe and could easily be separated from their
over it or can adapt it to new uses. The domesti- hulls. Over the next few millennia, people around
cation of wheat is a good example. the world used similar processes of evolution-
By recovering seeds from dif- ary change to transform many other
ferent archaeological sites and wild plants and animals into the
noticing changes in their char- crops and domesticated animals
acteristics over the centuries, we rely on today.
scientists have hypothesized In recent years, plant sci-
how wheat was altered by entists have begun making
humans over time. About hybrids of wheat with some
11,000 years ago, people of their wild relatives from
in the Middle East began the Middle East and else-
growing plants for food where. Using these hybrids,
rather than relying entirely they have bred wheat varieties
on the wild plants and ani- that are increasingly resistant
mals they could gather or hunt. to droughts, heat, and pests.
These early farmers began sav- Most recently, molecular biologists
ing seeds from plants with particu- have been identifying the genes in
larly favorable traits and planting those the DNA of plants that are responsible for
seeds in the next growing season. Through this their advantageous traits so that these genes can
process of “artificial selection,” they created a be incorporated into other crops. These advances
variety of crops with characteristics particularly rely on an understanding of evolution to analyze
suited for agriculture. For example, farmers the relationships among plants and to search for
over many generations modified the traits of the traits that can be used to improve crops.
evolution can result in both small and
large changes in populations of organisms.
Evolutionary biologists have discovered structures, biochemical processes and
pathways, and behaviors that appear to have been highly conserved within
and across species. Some species have undergone little overt change in their
body structure over many millions of years. At the level of DNA, some genes
that control the production of biochemicals or chemical reactions that are
essential for cellular functioning show little variation across species that are
only distantly related. (See, for example, the DNA sequences for two different
genes that are conserved in closely related as well as more distantly related
species that are described on pages 30 and 31.)
However, natural selection also can have radically different evolutionary
effects over different timescales. Over periods of just a few generations (or,
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in some documented cases, even a single generation), evolution produces
[microevolution:
relatively small-scale microevolutionary changes in organisms. For example,
Changes in the traits
many disease-causing bacteria have been evolving increased resistance to anti-
of a group of organ­
biotics. When a bacterium undergoes a genetic change that increases its ability
isms that do not result
to resist the effects of an antibiotic, that bacterium can survive and produce
in a new species.]
more copies of itself while nonresistant bacteria are being killed. Bacteria that
cause tuberculosis, meningitis, staph infections, sexually transmitted diseases,
and other illnesses have all become serious problems as they have developed
resistance to an increasing number of antibiotics.
Another example of microevolutionary change comes from
an experiment on the guppies that live in the Aripo River
on the island of Trinidad. Guppies that live in the river are
eaten by a larger species of fish that eats both juveniles and
adults, while guppies that live in the small streams feeding
into the river are eaten by a smaller fish that preys primarily
on small juveniles. The guppies in the river mature faster, are
smaller, and give birth to more and smaller offspring than the
guppies in the streams do because guppies with these traits
are better able to avoid their predator in the river than are
larger guppies. When guppies were taken from the river and
introduced into a stream without a preexisting population of
guppies, they evolved traits like those of the stream guppies
within about 20 generations.
Incremental evolutionary changes can, over what are usually very long Studies of guppies in
Trinidad have demon-
periods of time, give rise to new types of organisms, including new species.
strated basic evolution-
The formation of a new species generally occurs when one subgroup within a ary mechanisms.
species mates for an extended period largely within the subgroup. For exam-
ple, a subgroup may become geographically separated from the rest of the
species, or a subgroup may come to use resources in a way that sets them apart
from other members of the same species. As members of the subgroup mate
among themselves, they accumulate genetic differences compared with the rest
of the species. If this reproductive isolation continues for an extended period,
How long could it take to produce 1,000 generations?
How many generations might occur in a million years?
1 Generation 1,000 Generations Generations per 1 million years
Bacteria 1 hour to 1 day 1,000 hours (42 days) to 2.7 years 8.7 billion to 370.4 million
Pets: dog/cat 2 years 2,000 years 500,000
Humans 22 years 22,000 years 45,000
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members of the subgroup may no longer respond to court-
ship or other signals from members of the original population.
Eventually, genetic changes will become so substantial that the
members of different subgroups can no longer produce viable
offspring even if they do mate. In this way, existing species
can continually “bud off” new species.
Over very long periods of time, continued instances of
speciation can produce organisms that are very different from
their ancestors. Though each new species resembles the species
from which it arose, a succession of new species can diverge
more and more from an ancestral form. This divergence from
an ancestral form can be especially dramatic when an evolu-
tionary change enables a group of organisms to occupy a new
habitat or make use of resources in a novel way.
Consider, for example, the continued evolution of the tet-
rapods after limbed animals began living on land. As new species of plants
When tetrapods (such
as this sea turtle laying
evolved and covered the Earth, new species of tetrapods appeared with features
its eggs on a coastal
that enabled them to take advantage of these new environments. The early tetra-
beach) evolved the abil-
pods were amphibians that spent part of their lives on land but continued to lay
ity to lay hard-shelled
eggs, they no longer their eggs in the water or in moist environments. The evolution about 340 million
had to return to the
years ago of amniotic eggs, which have structures such as hard or leathery shells
water to reproduce.
The last common ances-
tor of the four-legged
animals living today
gave rise to amphibians
and was the predeces-
sor of reptiles. Birds and
mammals evolved from
different lineages of
ancient reptiles.
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Evolution in Industry: Putting Natural Selection to Work
The concept of natural selection has been
applied in many fields outside biology. For
example, chemists have applied principles of
natural selection to develop new molecules
with specific functions. First they create
variants of an existing molecule using chemi-
cal techniques. They then test the variants
for the desired function. The variants that
do the best job are used to generate new
variants. Repeated rounds of this selection
process result in molecules that have a greatly
enhanced ability to perform a given task.
This technique has been used to create new
enzymes that can convert cornstalks and
other agricultural wastes into ethanol with
increased efficiency.
and additional membranes that allow developing embryos to survive in dry
environments, was one of the key developments in the evolution of the reptiles.
The early reptiles split into several major lineages. One lineage led to
reptiles, including dinosaurs, and also to birds. Another lineage gave rise to
mammals between 200 million and 250 million years ago.
The evolutionary transition from reptiles to mammals is particularly well
documented in the fossil record. Successive fossil forms tend to have larger
brains and more specialized sense organs, jaws and teeth adapted for more
efficient chewing and eating, a gradual movement of the limbs from the sides
of the body to under the body, and a female reproductive tract increasingly
able to support the internal development and nourishment of young. Many of
the biological novelties seen in mammals may be associated with the evolution
of warm-bloodedness, which enabled a more active lifestyle over a much larger
range of temperatures than in the cold-blooded reptilian ancestors.
Then, between 60 million and 80 million years ago, a group of mammals
known as the primates first appeared in the fossil record. These mammals
had grasping hands and feet, frontally directed eyes, and even larger and
more complex brains. This is the lineage from which ancient and then modern
humans evolved.
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Scientists seek explanations of natural
phenomena based on empirical evidence.
Advances in the understanding of evolution over the past two centuries
provide a superb example of how science works. Scientific knowledge and
understanding accumulate from the interplay of observation and explanation.
Scientists gather information by observing the natural world and conducting
experiments. They then propose how the systems being studied behave in
general, basing their explanations on the data provided through their experi-
ments and other observations. They test their explanations by conducting
additional observations and experiments under different conditions. Other
scientists confirm the observations independently and carry out additional
studies that may lead to more sophisticated explanations and predictions
about future observations and experiments. In these ways, scientists continu-
ally arrive at more accurate and more comprehensive explanations of particu-
lar aspects of nature.
In science, explanations must be based on naturally occurring phenomena.
Natural causes are, in principle, reproducible and therefore can be checked
independently by others. If explanations are based on purported forces that
are outside of nature, scientists have no way of either confirming or disprov-
ing those explanations. Any scientific explanation has to be testable — there
must be possible observational consequences that could support the idea
but also ones that could refute it. Unless a proposed explanation is framed in a
way that some observational evidence could potentially count against it, that
explanation cannot be subjected to scientific testing.
Definition of Science
The use of evidence to construct testable explanations
and predictions of natural phenomena, as well as the
knowledge generated through this process.
Because observations and explanations build on each other, science is a
cumulative activity. Repeatable observations and experiments generate expla-
nations that describe nature more accurately and comprehensively, and these
explanations in turn suggest new observations and experiments that can be
used to test and extend the explanation. In this way, the sophistication and
scope of scientific explanations improve over time, as subsequent generations
of scientists, often using technological innovations, work to correct, refine, and
extend the work done by their predecessors.
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Is Evolution a Theory or a Fact?
vations and experiments that were not possible
It is both. But that answer requires looking more
previously.
deeply at the meanings of the words “theory”
One of the most useful properties of scientific
and “fact.”
theories is that they can be used to make predic-
In everyday usage, “theory” often refers to
tions about natural events or phenomena that have
a hunch or a speculation. When people say, “I
not yet been observed. For example, the theory of
have a theory about why that happened,” they
gravitation predicted the behavior of objects on the
are often drawing a conclusion based on frag-
Moon and other planets long before the activities
mentary or inconclusive evidence.
of spacecraft and astronauts confirmed them. The
The formal scientific definition of theory is
evolutionary biologists who discovered Tiktaalik
quite different from the everyday meaning of
(see page 2) predicted that they would find fossils
the word. It refers to a comprehensive explana-
intermediate between fish and limbed terrestrial
tion of some aspect of nature that is supported
animals in sediments that were about 375 million
by a vast body of evidence.
years old. Their discovery confirmed the prediction
Many scientific theories are so well estab-
made on the basis of evolutionary theory. In turn,
lished that no new evidence is likely to alter
confirmation of a prediction increases confidence in
them substantially. For example, no new evi-
that theory.
dence will demonstrate that the Earth does
In science, a “fact” typically refers to an obser-
not orbit around the Sun (heliocentric theory),
vation, measurement, or other form of evidence
or that living things are not made of cells (cell
that can be expected to occur the same way under
theory), that matter is not composed of atoms,
similar circumstances. However, scientists also use
or that the surface of the Earth is not divided
the term “fact” to refer to a scientific explanation
into solid plates that have moved over geologi-
that has been tested and confirmed so many times
cal timescales (the theory of plate tectonics).
that there is no longer a compelling reason to keep
Like these other foundational scientific theo-
testing it or looking for additional examples. In
ries, the theory of evolution is supported by so
that respect, the past and continuing occurrence of
many observations and confirming experiments
evolution is a scientific fact. Because the evidence
that scientists are confident that the basic com-
supporting it is so strong, scientists no longer ques-
ponents of the theory will not be overturned
tion whether biological evolution has occurred and
by new evidence. However, like all scientific
is continuing to occur. Instead, they investigate the
theories, the theory of evolution is subject to
mechanisms of evolution, how rapidly evolution can
continuing refinement as new areas of science
take place, and related questions.
emerge or as new technologies enable obser-
In science it is not possible to prove with absolute certainty that a given
explanation is complete and final. Some of the explanations advanced by sci-
entists turn out to be incorrect when they are tested by further observations or
experiments. New instruments may make observations possible that reveal
the inadequacy of an existing explanation. New ideas can lead to explana-
tions that reveal the incompleteness or deficiencies of previous explanations.
Many scientific ideas that once were accepted are now known to be inaccurate
or to apply only within a limited domain.
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However, many scientific explanations have been so thoroughly tested
that they are very unlikely to change in substantial ways as new observations
are made or new experiments are analyzed. These explanations are accepted
by scientists as being true and factual descriptions of the natural world. The
atomic structure of matter, the genetic basis of heredity, the circulation of blood,
gravitation and planetary motion, and the process of biological evolution by
natural selection are just a few examples of a very large number of scientific
explanations that have been overwhelmingly substantiated.
Science is not the only way of knowing and understanding. But science is a
way of knowing that differs from other ways in its dependence on empirical evidence
and testable explanations. Because biological evolution accounts for events
that are also central concerns of religion — including the origins of biological
diversity and especially the origins of humans — evolution has been a conten-
tious idea within society since it was first articulated by Charles Darwin and
Alfred Russel Wallace in 1858.
acceptance of the evidence for evolution
can be compatible with religious faith.
Today, many religious denominations accept that biological evolution has
produced the diversity of living things over billions of years of Earth’s his-
tory. Many have issued statements observing that evolution and the tenets of
their faiths are compatible. Scientists and theologians have written eloquently
about their awe and wonder at the history of the universe and of life on this
planet, explaining that they see no conflict between their faith in God and the
evidence for evolution. Religious denominations that do not accept the occur-
rence of evolution tend to be those that believe in strictly literal interpretations
of religious texts.
Science and religion are based on different aspects of human experience.
In science, explanations must be based on evidence drawn from examining the
natural world. Scientifically based observations or experiments that conflict
with an explanation eventually must lead to modification or even abandon-
ment of that explanation. Religious faith, in contrast, does not depend only
on empirical evidence, is not necessarily modified in the face of conflicting
evidence, and typically involves supernatural forces or entities. Because they
are not a part of nature, supernatural entities cannot be investigated by sci-
ence. In this sense, science and religion are separate and address aspects of
human understanding in different ways. Attempts to pit science and religion
against each other create controversy where none needs to exist.
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Excerpts of Statements by Religious Leaders
Who See No Conflict Between Their Faith and Science
Many religious denominations and individual religious leaders have issued
statements acknowledging the occurrence of evolution and pointing out
that evolution and faith do not conflict.
“[T]here is no contradiction between
an evolutionary theory of human
origins and the doctrine of God as
“[S]tudents’ ignorance about evolution will
Creator.”
seriously undermine their understanding
— General Assembly of the
of the world and the natural laws gov-
Presbyterian Church
erning it, and their introduction to other
explanations described as ‘scientific’ will
give them false ideas about scientific
methods and criteria.”
— Central Conference of American
Rabbis
“In his encyclical Humani Generis (1950), my predecessor Pius XII has already
affirmed that there is no conflict between evolution and the doctrine of the faith
regarding man and his vocation, provided that we do not lose sight of certain
fixed points. . . . Today, more than a half-century after the appearance of that
encyclical, some new findings lead us toward the recognition of evolution as more
than an hypothesis. In fact it is remarkable that this theory has had progressively
greater influence on the spirit of researchers, following a series of discoveries in
different scholarly disciplines. The convergence in the results of these independent
studies — which was neither planned nor sought — constitutes in itself a signifi-
cant argument in favor of the theory.”
— Pope John Paul II, Message to the Pontifical Academy of Sciences, October 22, 1996.
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Excerpts of Statements by Religious Leaders
Who See No Conflict Between Their Faith and Science
(continued)
“We the undersigned, Christian clergy from many different
traditions, believe that the timeless truths of the Bible and
the discoveries of modern science may comfortably coexist.
We believe that the theory of evolution is a foundational
scientific truth, one that has stood up to rigorous scrutiny
and upon which much of human knowledge and achieve-
ment rests. To reject this truth or to treat it as ’one theory
among others’ is to deliberately embrace scientific ignorance
and transmit such ignorance to our children. We believe that
among God’s good gifts are human minds capable of criti-
cal thought and that the failure to fully employ this gift is a
rejection of the will of our Creator. . . . We urge school board
members to preserve the integrity of the science curriculum
by affirming the teaching of the theory of evolution as a
core component of human knowledge. We ask that science
remain science and that religion remain religion, two very
different, but complementary, forms of truth.”
—“The Clergy Letter Project” signed by more than 10,000
Christian clergy members. For additional information, see
http://www.butler.edu/clergyproject/clergy_project.htm.
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Excerpts of Statements by Scientists
Who See No Conflict Between Their Faith and Science
Scientists, like people in other professions, hold a wide range of positions about
religion and the role of supernatural forces or entities in the universe. Some adhere
to a position known as scientism, which holds that the methods of science alone are
sufficient for discovering everything there is to know about the universe. Others
ascribe to an idea known as deism, which posits that God created all things and set
the universe in motion but no longer actively directs physical phenomena. Others
are theists, who believe that God actively intervenes in the world. Many scientists
who believe in God, either as a prime mover or as an active force in the universe,
have written eloquently about their beliefs.
“Creationists inevitably look for God in what science
has not yet explained or in what they claim science
cannot explain. Most scientists who are religious
look for God in what science does understand and
has explained.”
— Kenneth Miller, professor of biology at Brown
University and author of Finding Darwin’s God: A
Scientist’s Search for Common Ground Between God
and Religion. Quote is excerpted from an inter-
“In my view, there is no conflict in being view available at http://www.actionbioscience.
a rigorous scientist and a person who org/evolution/miller.html.
believes in a God who takes a personal
interest in each one of us. Science’s
domain is to explore nature. God’s “Our scientific understanding of the universe . . .
domain is in the spiritual world, a realm provides for those who believe in God a marvelous
not possible to explore with the tools and opportunity to reflect upon their beliefs.”
language of science. It must be examined
— Father George Coyne, Catholic priest
with the heart, the mind, and the soul.” and former director of the Vatican Observatory.
Quote is from a talk, “Science Does Not Need
— Francis Collins, director of the
God, or Does It? A Catholic Scientist Looks at
Human Genome Project and of
Evolution,” at Palm Beach Atlantic University,
the National Human Genome
January 31, 2006. Available at http://chem.tufts.
Research Institute at the National
edu/AnswersInScience/Coyne-Evolution.htm.
Institutes of Health. Excerpted
from his book, The Language of God:
A Scientist Presents Evidence for
Belief (p. 6).
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Science, evolution, and creationiSm